2005 OPEN FORUM Abstracts
Airway Pressure Release Ventilation Utilized in the Management of an ARDS Patient with COPD when conventional modes of ventilation were failing.
Bill Haire, RRT, Donald Wantuck MD. St. John's Mercy Health Systems, Springfield, MO 65804
Introduction: Airway Pressure Release Ventilation (APRV) has been used successfully in neonatal, pediatric, and adult population in patients with Adult Respiratory Distress Syndrome (ARDS) and Acute Lung Injury (ALI). APRV is a mode of ventilation that allows unrestricted spontaneous breathing throughout the patient's ventilatory cycle, and is consistent with lung protective strategies limiting ventilating pressures and over distention. Spontaneous breathing augments venous return and cardiac output. There is very little information on the use of APRV in patients with Chronic Obstructive Pulmonary Disease (COPD). We present a case report examining an ARDS patient with documented COPD.
Case Study: A sixty-two year old female with previous medical history of COPD, asthma, and bronchiectasis presents to the emergency department (ED) with a two-day history of increased shortness of breath. Further work up in the ED revealed extensive bilateral five-lobe infiltrate via portable chest X-ray, a temperature of 102, systolic blood pressure (SBP) 58/35, heart rate (HR) 117, respiratory rate (f) 38 and SpO2 67% on 15 lpm non-rebreathing mask. Patient was intubated, transferred to the medical ICU and placed on a Drager E-4 ventilator utilizing a volume-targeted mode (CMV+AutoFlow [AF]) maintaining a plateau pressure (Pplat) < 30cm/H2O. Arterial blood gas results drawn one hour after arrival to the MICU revealed a pH of 7.22, PaO2 of 82, PaCO2 of 50 on FiO2 of 1.0, PaO2/FiO2 ratio 82, mean airway pressure (MAP) 10. Over the course of the next 5 days slight adjustments were made to maintain ventilation and normocarbia was easily maintained; however, there was no improvement in oxygenation. ABG results drawn 114 hours after the initiation of volume-targeted ventilation, Pplat maintained < 30 cmH2O and MAP of 16 cm/H2O, and revealed pH 7.30, PaO2 52, PaCO2 45, P/F ratio 52 torr. The decision was made to transition to APRV to be managed by respiratory departmental guidelines. Initial APRV settings were Time High (THigh) 4.0 sec/Time Low (Tlow) 0.9 sec/ Pressure High (PHigh) 26 cm/H2O/Pressure Low (PLow) 0 cm/H20, with resulting MAP 25 cm/H2O. Careful attention was paid to the setting of Tlow to terminate the release time prior to expiratory flow reaching baseline. It is the goal of the departmental guidelines to terminate the release time once expiratory flow has reached 50% of the peak expiratory flow rate. Seven hours after the initiation of APRV ventilation had maintained and the P/F ratio had improved 103 torr. Of note, the increase of MAP by nine cm/H20 had no deleterious effect on the patient's blood pressure. Twenty-four hours after being placed on APRV the patient's P/F ratio was 152 torr with settings of THigh 5.0 sec/ Tlow 1.0 sec/ PHigh 24 cm/H2O/ PLow 0 cm/H2O. The P/F ratio continued to improve to 243 torr within 48 hours of transitioning to APRV. Three days after the initiation of APRV the settings were THigh 7.5 sec/ Tlow 1.5 sec/ PHigh 14 cm/H2O / PLow 0 cm/H2O/ FiO2 0.4. Patient vital signs on these settings HR 87, f 18, SBP 117/56, SpO2 97%. The patient was transitioned to 10 cm/H2O continuous positive airway pressure (CPAP) with 4 cm /H2O pressure support ventilation and extubated to 4 lpm nasal O2 the following morning. After undergoing in-patient pulmonary rehab for another 24 days, the patient was discharged to home with no obvious deficits.
Conclusion: APRV has not been researched as thoroughly as other modes. Information is especially lacking for APRV utilized with patients with documented COPD. APRV has been shown to improve gas exchange, facilitate spontaneous breathing, and possibly reduce ventilator days. Due to short release times generally utilized with APRV, there is a concern that it might potentiate air trapping in patients with COPD. Based on the results of this case presentation it is possible to safely and successfully manage this type of patient, as long as close observation of the expiratory flow pattern and patient's respiratory pattern occurs. Further research in this area is warranted and should be conducted.